1. Field of the Invention
Various embodiments of the invention relate to ultrasonic flow meters. More particularly, various embodiments of the invention related to driver configurations for reducing transit time errors in measurement of ultrasonic signals of an ultrasonic flow meter.
2. Description of the Related Art
Ultrasonic flow meters are a class of flow meters that determine volumetric flow of a fluid within a conduit using ultrasonic signals propagated through the fluid. For example, an ultrasonic flow meter may measure the transit time of an upstream traveling ultrasonic signal along a particular path, measure transit time of a downstream traveling ultrasonic signal along the path. From these measurements, a “delta time” is determined as the difference between the upstream and downstream transit times. From the delta time, the average flow rate of the fluid may be determined, and from the flow rate a volumetric flow may be calculated. Thus, measuring an accurate delta time is important to determining an accurate flow rate.
The measured transit time of an ultrasonic signal between a transducer pair has at least two major components: an “actual time of flight” of the ultrasonic signal in the fluid between the faces of the transducers; and a “delay time” that comprises the difference between the measured transit time and the actual time of flight. Delay time may thus encompass: propagation delays between a control processor and the transducer drivers; propagation delay between transducer drivers and the transducers as transmitters; propagation delays between transducers as receivers and the receiving electronics; propagation delays between the receiving electronics and the processor; and delays associated with control electronics with finite response times attempting to measure elapsed time. In ultrasonic meters measuring flow of gaseous fluids, the delay time may have a small effect in the overall fluid flow calculations. However, in ultrasonic meters measuring flow in fluids with high density, such as liquids, the delay time may have a large effect.
Thus, a system which reduces errors associated delay time variables would be desirable.